In general, a refrigerator or an air conditioner, as small-sized home alliances, is provided with a compressor for compressing a refrigerant. A representative motor for the compressor which drives the compressor is a well-known induction motor. The induction motor includes a stator on which a coil is wound, a rotor having conductors in the form of a squirrel cage and rotatably inserted inside of the stator, and a rotational shaft press-fitted in the center of the is rotor for carrying a rotational force, generated by an interaction between a rotation magnetic field generated by an alternating current (AC) flowing in the coil of the stator and an induction current generated by the rotor, to a compression unit of the compressor.
Each of the stator and rotor is configured such that plural sheets of thin stator core are stacked together to be welded. The stator core of the stator includes a yoke portion formed in an approximately annular shape and implementing a moving path of magnetism, a plurality of tooth portions protruded from an inner circumferential surface of the yoke portion with a certain gap and having the coil wound therearound, and a slot portion recessed between the tooth portions so as to allow the coil wound around the tooth portions to be inserted therein.
The coil is widely implemented using copper (Cu) having high conductivity. The conductivity indicates how well a current flows in a material. However, it cannot be said that high conductivity always means many number of electrons flowing. The number of electrons is in proportion to a current. Accordingly, if conductivity is low but the current is the same, it can be said that the number of electrons are the same. However, with respect to the same current, the higher conductivity can lower heat loss occurred in the material itself. A well-known material having the highest conductivity is argentums (Ag), but such Ag is expensive. Thus, copper requiring a relatively low price and having high conductivity is used for the motor for the compressor.
However, a demand of a compressor which has various functions and low price is increased as a technique for the compressor is greatly improved as well as the long history of its development. In spite of this trend, for the coil which occupies a great portion of a fabricating cost for the motor for the compressor, because it greatly influences the efficiency of the motor, a material having the high conductivity such as the copper is still used in spite of the burden of its cost.